Geoff,
Yes, I have experienced this phenomenon.
Interpretation depends, of course, on what kinds of pots you're referring
to and whether you know enough about the historical context of their
disposal.
For example, I've recently recovered a number of chamber pots which were
probably intact when they were discarded, from a 19th C to turn of the
century privy.  I believe these to be directly related to the fact that
this resort community installed indoor plumbing and closed off the privy
with a variety of objects which were no longer needed along with the usual
spare bricks, cobbles and borrowed soil, around 1900-1910.  Spring cleaning
of a sort, but not really seasonal.  The inference is supported by an
advertisement in an early twentieth C magazine which mentions electricity
and indoor plumbing in the community.

best,

Matt